Higher death rates among blacks in the U.S. due to heart disease, cancer, homicide, diabetes and childbirth conditions drive a persistent gap in life expectancy for the group compared with whites, a government study found.

One of the biggest questions in determining the future sustainability of our health-care system is this: Will the 21st century witness as large an increase in the average life expectancy of the rich countries -- 30 to 40 years -- as occurred during the last century?